3. How many oxygen atoms are there in one formula unit of Ca3(PO4)2? (A)2(B)4 (C)6 (D)8 (E) none of these

9. Calculate the molality of C2H5OH in a water solution that is prepared by mixing 50.0 mL of C2H5OH with 100.0 mL of H2O at 20℃. The density of the C2H5OH is 0.789 g/mL at 20℃. (C2H5OH: 46.07 g/mol. Density of H2O is 1 g/cm3). (A) 0.086 m (B) 0.094 m (C) 1.24 m (D) 8.56 m (E) none of these